Data · Law · Reference
Utah ADU Laws by City: 2026 Rules, Data & SB 284 Status
By Utah ADU Builders Research
State detached-ADU requirement checked: . City records: individually dated below.
Utah ADU rules combine state requirements with local development standards. Utah Code §10-21-304 took effect on October 1, 2026. It requires a specified municipality to permit a detached accessory dwelling unit on a lot or parcel of at least 11,000 square feet that contains a single-family dwelling, where that dwelling is a permitted use. This state requirement does not establish that a city’s ordinance has been updated or that a particular property is approved. The jurisdiction records below retain their individual verification dates.
“Specified municipality” is not a population line, and this is where most summaries go wrong. It is a two-part legal test: a city of the first, second, third, or fourth class, or a city of the fifth class with 5,000 or more residents that sits in a county of the first, second, or third class. Ten of Utah’s 29 counties meet that second condition. A 6,000-person city in Sanpete or Carbon County is not covered.
Key verified finding — October 3, 2026
The statute contains an affirmative duty almost nobody is discussing: every covered city must build a process for converting an existing legally constructed accessory structure — a detached garage, a shop, an outbuilding — into a dwelling. That is not a permission. It is a requirement of the ordinance itself. Source: Utah Code § 10-21-304(2)(b).
The one-screen answer
| Your question | The statutory answer | What your city still controls |
|---|---|---|
| Can I create an internal ADU? | A qualifying internal ADU is a permitted use in any area zoned primarily for residential use, subject to building, health and fire codes and the conditions § 10-21-303 expressly authorizes. | One extra parking stall, a rental license, a 30-day minimum rental, an owner-occupancy condition, exclusion on lots of 6,000 sq ft or less, and a mapped exclusion district covering up to 25% of residential land. |
| Can I build a detached ADU? | From October 1, 2026, a specified municipality must permit one on a qualifying lot of 11,000 sq ft or larger. Cities may also allow them on smaller lots. | Size, dimensions, height, lot coverage, setbacks, design compatibility, front-yard placement, owner occupancy, utility capacity, and a 90-day minimum rental. |
| Does every city over 5,000 qualify? | No. | Municipal class comes first; county class matters only for fifth-class cities. |
| Does 11,000 sq ft guarantee approval? | No. | Setbacks, height, buildable area, utility capacity and building and fire codes still control. |
| Does this reach unincorporated county land? | No. | § 10-21-304 applies to specified municipalities. County land follows county statutes and county ordinance. |
Source: Utah Code §§ 10-21-101, 10-21-303, 10-21-304 (Utah State Legislature). Verified by Utah ADU Builders Research, October 3, 2026.
What is the difference between an internal and a detached ADU?
Answer capsule
Utah law treats the two types under separate statutes with materially different rules. Getting the type wrong means reading the wrong statute.
The definitions live in Utah Code § 10-21-101, and one detail inside them matters more than most people realize.
An internal accessory dwelling unit is a unit created (a) within a primary dwelling, (b) within that dwelling’s footprint at the time the unit is created, and (c) for the purpose of offering a long-term rental of 30 consecutive days or longer.
A primary dwelling is a single-family dwelling that is detached and occupied as the primary residence of the owner of record. It includes an attached garage if the garage is habitable space connected by a common wall.
Read those together and the consequence is concrete: the statewide permitted-use protection for internal ADUs only attaches to an owner-occupied, detached single-family home. Owner occupancy is not merely something cities are allowed to require — it is built into the definition of the dwelling the protection applies to. A rental house, a townhome, or a duplex is outside the guarantee from the start.
A detached accessory dwelling unit is an ADU not attached to or within a primary detached single-family dwelling, located on the same lot or parcel.
Source: Utah Code § 10-21-101(9), (16), (21). Verified October 3, 2026.
Citation note
A number of Utah ADU pages and municipal codes still cite § 10-9a-530 for the internal ADU law. That section was renumbered and amended to § 10-21-303 by Chapter 15, 2025 First Special Session. If a source still points to the old number, it has not been reviewed since the recodification.
What can your city actually do to an internal ADU?
Answer capsule
Utah Code § 10-21-303 makes a qualifying internal ADU a permitted use and bars municipalities from regulating the unit’s size relative to the primary dwelling, total lot size, street frontage, or internal connectivity. It then enumerates the specific conditions a municipality may impose.
The 25% exclusion district is the least-known provision in Utah ADU law. A city may draw a map and prohibit new internal ADUs inside it, so long as the mapped area stays within a quarter of the city’s residentially zoned land. Lehi does exactly this: Development Code § 26.030(D) states that ADUs “shall not be allowed in any areas identified on the ADU Restricted Area Map,” and the city has publicly tied those exclusions to limited utility capacity. There is no equivalent area-based exclusion for detached ADUs — the 25% and 67% districts apply to internal units only.
| What a municipality may do | The statutory limit | Subsection |
|---|---|---|
| Prohibit a separate utility meter | Authorized; no numeric limit stated | (3)(a) |
| Require a design that preserves the single-family appearance | Authorized; no numeric limit stated | (3)(b) |
| Require additional on-site parking | One space only — and none may be required if the land use ordinance already requires four off-street spaces | (3)(c)(i) |
| Require replacement of garage or carport parking converted to habitable ADU space | Authorized | (3)(c)(ii) |
| Prohibit an internal ADU inside a mobile home | As defined in § 57-16-3 | (3)(d) |
| Require a permit or license to rent the unit | Authorized | (3)(e) |
| Prohibit internal ADUs in a mapped zoning district | The district may cover 25% or less of the municipality's total residentially zoned area — and the city may not prohibit newly constructed internal ADUs with final plat approval dated on or after October 1, 2021 that comply with applicable regulations | (3)(f)(i) |
| The same, at 67% or less | Only if the main campus of a state or private university with 10,000 or more students is located in the municipality | (3)(f)(ii) |
| Prohibit if the primary dwelling is served by a failing septic tank | Authorized | (3)(g) |
| Prohibit if the lot is 6,000 sq ft or less | Authorized — note this is "or less," so a lot at exactly 6,000 sq ft may be excluded | (3)(h) |
| Prohibit rentals of fewer than 30 consecutive days | Authorized | (3)(i) |
| Prohibit rental where the dwelling is not the owner's primary residence | Authorized | (3)(j) |
| Place a lien for violations | Up to $100 per day after the cure period expires, following written notice, at least 14 days to cure a short-term-rental violation or 30 days otherwise, and a hearing if the owner objects in writing | (3)(k), (4) |
| Record a notice with the county recorder | Authorized | (3)(l), (5) |
Source: Utah Code § 10-21-303, effective November 6, 2025 (Utah State Legislature). Read in full and verified by Utah ADU Builders Research, October 3, 2026.
What does Utah Code § 10-21-304 require, exactly?
Answer capsule
Section 10-21-304, enacted by S.B. 284 and effective October 1, 2026, requires a specified municipality to adopt a land use regulation permitting a detached ADU on any lot of 11,000 sq ft or larger containing a single-family dwelling where single-family dwellings are a permitted use.
The mandate — § 10-21-304(1)
A specified municipality shall adopt a land use regulation permitting a detached ADU on any lot or parcel that is 11,000 square feet or larger and contains a single-family dwelling, if that single-family dwelling is a permitted use there. Nothing stops a city from permitting detached ADUs on smaller lots, and several already do.
What the regulation must include — § 10-21-304(2)
| Requirement | Text |
|---|---|
| Building codes | The regulation shall require a detached ADU to comply with all applicable building, health and fire codes. |
| Conversion process | The regulation shall include a process for the owner of a legally constructed accessory structure to convert that structure to a detached ADU, subject to applicable dwelling and accessory-structure setback requirements and building, health and fire codes. This is an affirmative drafting duty, not a permission. Every covered city must publish a route from existing outbuilding to dwelling. |
Source: Utah Code § 10-21-304(2), effective October 1, 2026. Verified October 3, 2026.
What a city may not do — § 10-21-304(3)
| Prohibition | Subsection |
|---|---|
| Require a conditional use permit for a detached ADU in a primarily residential zone | (3)(a) |
| Require more than two on-site parking spaces assigned to a detached ADU of 650 sq ft or larger | (3)(b) |
| Require more than one on-site parking space assigned to a detached ADU smaller than 650 sq ft | (3)(c) |
| Impose design standards that conflict with § 10-20-618 | (3)(d) |
Source: Utah Code § 10-21-304(3). Verified October 3, 2026.
What a city may still do — § 10-21-304(4)
| Authority | Subsection |
|---|---|
| Require conformance with land use regulations governing structure size, dimension, height, and maximum lot coverage | (4)(a)(i) |
| Require conformance with setbacks accounting for proximity to property lines and other structures, easements, window orientation, massing, or other elements | (4)(a)(ii) |
| Require the unit be designed consistent with the design of the single-family dwelling | (4)(a)(iii) |
| Prohibit a detached ADU larger than the single-family dwelling on the same lot | (4)(b)(i) |
| Prohibit placement within a public utility or other recorded easement | (4)(b)(ii) |
| Prohibit placement in a front-yard area | (4)(b)(iii) |
| Prohibit rental for fewer than 90 consecutive days | (4)(b)(iv) |
| Require the owner to reside in the single-family dwelling or the detached ADU | (4)(c) |
| Require on-site replacement of parking lost when a detached garage is converted | (4)(d) |
| Prohibit more than one ADU per lot or parcel | (4)(e) |
| Prohibit a detached ADU where it will not have adequate access to a required utility service that is a project improvement, or where a system improvement lacks sufficient capacity | (4)(f) |
Source: Utah Code § 10-21-304(4). Verified October 3, 2026.
What the section does not disturb — § 10-21-304(5)
- Regulation of detached accessory buildings that are not dwelling units
- Prohibitions or restrictions in a development agreement signed by a municipality on or before May 6, 2026
- Any other land use regulation or administrative action not prohibited by law
That development-agreement carve-out matters in Utah more than it would in most states. Large master-planned communities operate under signed development agreements, and a restriction inside one of those agreements survives October 1. If you live in a master-planned community, the agreement — not the city ordinance — may be the controlling document.
Source: Utah Code § 10-21-304, effective October 1, 2026, enacted by Chapter 166, 2026 General Session. Read in full and verified by Utah ADU Builders Research, October 3, 2026.
Two clarifications on common misreports
First, § 10-21-304 does not bar cities from setting a maximum square footage. Subsection (4)(a)(i) expressly preserves regulations governing structure size and dimension, and (4)(b)(i) separately allows a cap at the size of the primary home. A local numeric size cap is lawful.
Second, the 90-day minimum rental term for detached units is real statutory text at (4)(b)(iv) — a different and longer floor than the 30-day term § 10-21-303(3)(i) authorizes for internal units.
Which Utah cities are specified municipalities?
Answer capsule
Defined at Utah Code § 10-21-101(25): a city of the first, second, third, or fourth class, or a city of the fifth class with a population of 5,000 or more located within a county of the first, second, or third class. Towns, and fifth-class cities in smaller counties, are outside the mandate.
Applying the test takes two published tables.
Municipal class — Utah Code § 10-2-301
| Class | Population |
|---|---|
| First class | 100,000 or more |
| Second class | 65,000–99,999 |
| Third class | 30,000–64,999 |
| Fourth class | 10,000–29,999 |
| Fifth class | 1,000–9,999 |
| Town | Under 1,000 |
Source: Utah Code § 10-2-301 (Utah State Legislature). Verified October 3, 2026.
County class — Office of Legislative Research and General Counsel, June 3, 2025
| County class | Population threshold | Counties |
|---|---|---|
| First | 1,150,000+ | Salt Lake |
| Second | 260,000–1,149,999 | Davis, Utah, Weber |
| Third | 40,000–259,999 | Washington, Box Elder, Cache, Iron, Summit, Tooele |
Source: Utah State Legislature, Office of Legislative Research and General Counsel, June 3, 2025. Populations are U.S. Census estimates as of July 1, 2024; thresholds set by § 17-50-501 as amended by H.B. 176 (2025). Verified by Utah ADU Builders Research, October 3, 2026.
Ten counties satisfy the second clause. A city of 5,000–9,999 residents qualifies only if it sits in Salt Lake, Davis, Utah, Weber, Washington, Box Elder, Cache, Iron, Summit, or Tooele County. A city of that size in Carbon, Duchesne, Juab, Millard, Morgan, San Juan, Sanpete, Sevier, Uintah, Wasatch, Beaver, Emery, Garfield, Grand, Kane, Daggett, Piute, Rich, or Wayne County is not a specified municipality.
Important legal wrinkle
A municipality retains its legal classification until a class change becomes effective through the lieutenant governor’s certification process under § 10-2-302. Any covered-municipality count built from population estimates alone is an approximation of legal status, not a determination of it.
Utah ADU laws by city: verified jurisdiction records
Answer capsule
Each record identifies an adopted code, official published guidance, proposal, or reported activity and carries its source-check date. A source check documents what was reviewed on that date; it does not certify later amendments or present-day compliance. An official proposal is not adopted law, and reported activity is not a legal source. Utah frost depth by city
Lehi
Source record checked October 3, 2026; current adopted rule not recertifiedImplementing ordinance adopted July 14, 2026. Lehi is the clearest example we have found of a Utah city that has already rewritten its code to the new state floor.
| Standard | Rule |
|---|---|
| Detached ADU minimum lot | 11,000 sq ft (§ 26.040, amended 07/14/2026) |
| Maximum size | Finished living area must be less than the primary home's square footage |
| Minimum dwelling area | 300 sq ft |
| Placement | Side or behind the primary dwelling; at least 6 feet from it; permanent foundation |
| Setbacks (built after 12/31/2020) | Within 5 feet of a side or rear line if that wall has no windows or two opaque windows of 2 sq ft or less each; 10 feet if larger windows, for a one-story structure up to 20 feet; primary-dwelling setbacks for any two-story structure or one over 20 feet |
| Conversion of pre-2021 accessory buildings | Permitted at 300 sq ft minimum, no garage required, 5 feet from the property line and 6 feet from the primary dwelling |
| Parking | The current published code says two off-street stalls above 650 sq ft and one below 650 sq ft, in addition to the primary dwelling’s parking; 9×20 ft per stall. It does not expressly resolve exactly 650 sq ft. State law caps assigned ADU spaces at two for a unit of 650 sq ft or larger. Ask Lehi how it applies the boundary and layout rules. |
| Utilities | All services must connect to the primary dwelling |
| Access | All-weather emergency access, minimum 12 feet wide |
| Address | Separate address: the primary address plus one-half |
| Units per lot | One; internal or detached, not both. Switching requires a new application |
| Owner occupancy | Required, by affidavit recorded against the property (§ 26.030(A), applied to detached units by § 26.040(1)(l)) |
| Internal ADU minimum lot | 6,000 sq ft |
| Internal ADU exclusions | Not allowed in areas on the ADU Restricted Area Map (§ 26.110) |
| Short-term rentals | An ADU permit and a short-term-rental permit may both be held, but only one may be active at a time |
| Impact fees | § 26.030(G) requires all applicable fees, including impact fees — but § 11-36a-202(2)(a)(vi) bars an impact fee on construction of an internal ADU within an existing primary dwelling |
Source: Lehi City Development Code Chapter 26 PDF, §§ 26.030, 26.040, 26.070, 26.110. Detached-ADU section amended July 14, 2026. Current published code checked October 3, 2026.
Unresolved gap in Lehi's own code
Section 26.040 now permits detached ADUs on lots of 11,000 sq ft. Section 26.070's maximum-height table — untouched by the July 14 amendment — still contains a detached-ADU row conditioned on a 22,000 sq ft lot. For a detached ADU on a lot between 11,000 and 21,999 sq ft, the table does not expressly say which row governs. Anyone designing a two-story unit on a lot in that range should get the answer in writing from Lehi planning before drawing.
Salt Lake City
Source record checked July 18, 2026; current adopted rule not recertifiedPermits detached ADUs by right with no minimum lot size. Salt Lake City eliminated conditional use requirements for ADUs in 2023 (Ordinance 17-23). Its rules are materially more permissive than the state floor now in effect.
| Standard | Rule |
|---|---|
| Conditional use permit | Not required. ADUs approved as conditional uses before April 4, 2023 are legal conforming uses |
| Minimum lot size | None (§ 21A.40.200.N.1) |
| Detached ADU maximum gross floor area | 1,000 sq ft (§ 21A.40.200.J.1). Basements used only for storage with no internal circulation, loft space under 7 feet, and stairs serving a second-level unit are excluded |
| Internal ADU maximum | None, provided the building meets the underlying zone's standards |
| Height | 17 feet, increasable to 24 feet for a pitched roof or 20 feet for a flat roof if side and rear setbacks increase one foot for each foot above 17. If the unit sits fully within the buildable area, it may reach the principal building's permitted height for the zone |
| Setbacks | Rear 3 ft; side 3 ft; corner side 20% of lot width or 10 ft, whichever is less. A converted accessory building may keep its existing setbacks unless the conversion includes an expansion |
| Placement | Not permitted in the front yard. Interior side yard permitted behind the rear facade of the principal building |
| Parking | One stall for the ADU, waived if the zone has no off-street minimum, if the property already has a surplus accessible stall, if within one-quarter mile of a public transit stop, or within one-half mile of a city-designated bicycle lane or path |
| Owner occupancy | Required. Qualifying owner-occupants include a deed owner, a relative by blood, marriage or adoption, or a family-trust trustor. Exceptions for bona fide temporary absence of 3 years or less, or placement in a hospital, nursing home or assisted-living facility |
| Recorded covenant | Required, on a city-attorney-approved form, recorded with the Salt Lake County Recorder before final inspection. Must describe both structures, allocate parking, and state that neither may be used as a short-term rental |
| Short-term rentals | Prohibited |
| Density | An ADU does not count toward the zone's permitted density |
Source: Salt Lake City Code § 21A.40.200 (Ord. 17-23, 2023; Ord. 53-18, 2018), via American Legal Publishing. Read and verified by Utah ADU Builders Research, July 18, 2026.
Planning an ADU here? Our Salt Lake City ADU builder guide compares project paths and shows what to check before requesting a builder review.
Ogden
Source record checked July 18, 2026; current adopted rule not recertified800 sq ft cap; ADU permit voids on sale of the property.
| Standard | Rule |
|---|---|
| Units per lot | One, on a lot containing a single-family dwelling |
| Owner occupancy | Required; the owner must occupy the main home or the ADU as a permanent principal residence |
| Occupancy limit | The non-owner-occupied unit is capped at two adults |
| Detached ADU size | Not less than 300, not more than 800 sq ft |
| Lot coverage | Detached units and accessory buildings combined may not occupy more than 25% of the rear yard |
| Parking | The dwelling must have its required two off-street spaces; no additional parking is required for the ADU |
| Appearance | Single-family appearance retained; any new entrance must be on the side or rear |
| Permit transfer | A change of property ownership voids the ADU permit. A new permit must be applied for |
| Recording | The city records the ADU certificate with the Weber County Recorder |
Source: Ogden City Code § 15-13-39 (Ord. 2016-2; amended by Ord. 2024-12, May 7, 2024), via American Legal Publishing, together with the city's ADU permit application. Verified by Utah ADU Builders Research, July 18, 2026.
Planning an ADU here? Our Ogden ADU builder guide explains project paths, builder checks and the questions to take to a contractor.
Cottonwood Heights
Source record checked July 18, 2026; current adopted rule not recertifiedConditional use path for detached ADUs; $1,100 permit. The city's official ADU page still frames its entire framework as a response to H.B. 82 (2021). We found no published amendment addressing § 10-21-304.
| Standard | Rule |
|---|---|
| Internal ADU | Permitted use on lots of 6,000 sq ft or more, in R-1, RR-1 and F-1 zones |
| Detached ADU | Conditional use in R-1, RR-1 and F-1 zones |
| Owner occupancy | Required; the record owner must occupy the primary dwelling or the ADU as a permanent residence, with proof at application |
| Parking — internal ADU | Base 2 stalls for the property, plus 1. No tandem stalls |
| Parking — detached ADU | Base 2 stalls, plus 2 (four total). No tandem stalls. Not permitted in the front yard |
| Short-term rentals | Prohibited (CH Code § 19.75.050.B) |
| ADU license fee | $100 |
| Conditional use permit fee (detached only) | $1,100 |
| Building permit fee | Varies by scope |
Source: Cottonwood Heights official Accessory Dwelling Units page (cottonwoodheights.utah.gov). Read and verified by Utah ADU Builders Research, July 18, 2026.
Provo
Official proposal / Reported activityProvo permits owner-occupied ADUs by right inside a defined ADU Overlay. In June 2026 the city published an eligibility-expansion page and parcel map showing its existing overlay alongside parcels the city identified as meeting the detached-ADU criteria.
As of July 15, 2026, the Provo City Council had discussed the issue in work meetings but had not sent it to the planning commission or taken a vote. Provo’s official ADU page carries a notice that content may change because of S.B. 284. No final implementing ordinance was verified in our source set as of July 18, 2026.
Sources: Provo City ADU page and June 2026 eligibility-expansion notice; Daily Herald, July 15, 2026. Verified July 18, 2026.
Orem
Official proposalOrem’s July 14, 2026 City Council agenda included a detached-ADU update, and its July 15 Planning Commission notice scheduled a public hearing on a text amendment establishing detached-ADU regulations. Reporting indicates the proposal would bar detached ADUs from front yards and prohibit short-term rental use. No adopted implementing ordinance was verified as of July 18, 2026.
Sources: Orem City Council and Planning Commission notices, July 2026; Daily Herald, July 15, 2026. Verified July 18, 2026.
River Heights
Official proposal — outside mandateRiver Heights, in Cache County, circulated an ADU code draft in 2026 that would continue to treat an external ADU as a conditional use. Cache is a third-class county, but River Heights has fewer than 5,000 residents — so under § 10-21-101(25)(b) it does not appear to be a specified municipality, and § 10-21-304 would not reach it.
We include it because it demonstrates the practical stakes of the two-part test. A city outside the definition may lawfully keep a conditional use requirement that a covered city may not.
Sources: River Heights ADU code draft (riverheights.gov), city record checked July 18, 2026; classification test against Utah Code §§ 10-2-301 and 10-21-101(25) checked October 3, 2026.
Unincorporated Salt Lake County
Source record checked July 18, 2026; county rule and reported data not recertifiedSection 10-21-304 applies to specified municipalities. Property outside municipal boundaries remains subject to county statutes and county ordinance — in Salt Lake County, County Code Chapter 19.15.
A 2024 presentation by Municipal Services District Planning and Development Services, prepared for the county’s moderate income housing implementation work, reported that two ADUs in unincorporated Salt Lake County had received both land use and building permit approval since 2021. The presentation reports approvals rather than completed units, and does not establish a causal relationship between the 2021 internal-ADU law and that count.
Source: Salt Lake County Municipal Services District Planning and Development Services, “Recommended Amendments to County Code Chapter 19.15,” 2024 Moderate Income Housing Implementation (published via Utah’s public notice website). Verified July 18, 2026.
Utah ADU owner-occupancy requirements by city
Answer capsule
Utah does not impose one owner-occupancy answer statewide. For internal ADUs, owner occupancy is embedded in the statutory definition of “primary dwelling.” For detached ADUs, § 10-21-304(4)(c) allows a city to require the owner to live in either unit. The operative rule is local, and the details differ.
| Jurisdiction | Requirement | Notable detail |
|---|---|---|
| Salt Lake City | Required | Deed owner, relative by blood/marriage/adoption, or family-trust trustor qualifies. Exceptions for duplex/multi-family/non-residential principal uses, a bona fide absence of 3 years or less, or placement in a care facility |
| Lehi | Required | Recorded affidavit against the property; applies to detached units through § 26.040(1)(l) |
| Ogden | Required | Owner must occupy main home or ADU as permanent principal residence; permit voids on sale |
| Cottonwood Heights | Required | Proof of owner occupancy required at application |
Source: municipal codes and official city guidance as cited in each jurisdiction record above; city-source dates are listed per jurisdiction. State-law provisions were checked October 3, 2026.
Utah ADU parking requirements by city
Answer capsule
State law caps what a city may require, and the caps differ by unit type. For internal ADUs, § 10-21-303(3)(c)(i) permits one additional space, and none at all where the ordinance already requires four off-street spaces. For detached ADUs from October 1, 2026, § 10-21-304(3)(b)–(c) permits at most two assigned spaces at 650 sq ft or larger and at most one below that size.
| Jurisdiction | Internal ADU | Detached ADU |
|---|---|---|
| Statutory ceiling | 1 additional space; none if the ordinance already requires 4 off-street spaces | 2 assigned spaces at 650 sq ft or larger; 1 below 650 sq ft |
| Lehi | 1 stall, not tandem, 9×20 ft | Published code: 2 stalls above 650 sq ft, 1 below; exactly 650 is not expressly resolved. State cap: 2 assigned ADU spaces at 650 sq ft or larger. Verify the boundary and layout with planning staff. |
| Salt Lake City | 1 stall, waived near transit, near a designated bike route, in zones with no minimum, or where a surplus accessible stall exists | Same |
| Cottonwood Heights | Base 2 for the property, plus 1 | Base 2, plus 2. Not permitted in the front yard |
| Ogden | The dwelling's required 2 off-street spaces; none added for the ADU | Same |
Source: Utah Code §§ 10-21-303, 10-21-304 checked October 3, 2026; municipal codes and official guidance retain their individual source dates.
Utah ADU short-term rental rules by city
Answer capsule
The two ADU types have different statutory floors. A municipality may prohibit renting an internal ADU for fewer than 30 consecutive days under § 10-21-303(3)(i), and may prohibit renting a detached ADU for fewer than 90 consecutive days under § 10-21-304(4)(b)(iv). Local ordinances may be stricter than either floor, and several are.
| Jurisdiction | Rule |
|---|---|
| Salt Lake City | Prohibited. The required recorded covenant must state that neither the ADU nor the principal structure may be used as a short-term rental |
| Cottonwood Heights | Prohibited (CH Code § 19.75.050.B) |
| Lehi | A homeowner may hold both an ADU permit and a short-term-rental permit, but only one may be active at a time |
Source: Utah Code §§ 10-21-303(3)(i), 10-21-304(4)(b)(iv) checked October 3, 2026; municipal codes and official guidance retain their individual source dates.
Published Utah ADU permit fees found so far
Answer capsule
Utah does not set a statewide ADU fee schedule. State law prohibits one specific charge: under § 11-36a-202(2)(a)(vi), no political subdivision may impose an impact fee on development activity consisting of the construction of an internal accessory dwelling unit within an existing primary dwelling. That exemption does not extend to detached units.
| Jurisdiction | Internal ADU | Detached ADU |
|---|---|---|
| Cottonwood Heights | $100 license + building permit (varies by scope) | $100 license + $1,100 conditional use permit + building permit (varies) |
| Lehi | Building permit and other applicable local fees; ADU license required while rented; amounts not published in the code | Same, plus applicable impact fees |
| Salt Lake City | Building permit; zoning certificate required; amounts not published in the code section | Same |
| Ogden | No clear public amount found on the pages we read | No clear public amount found on the pages we read |
Source: Utah Code § 11-36a-202(2)(a)(vi) checked October 3, 2026; official city fee information retains its source date in each jurisdiction record. “No clear public amount found” means exactly that — not that the fee is zero.
On Lehi’s impact-fee language
Section 26.030(G) requires an ADU applicant to pay “all applicable fees, including impact fees.” A general municipal code provision does not authorize a charge state law prohibits: § 11-36a-202(2)(a)(vi) bars an impact fee on construction of an internal ADU within an existing primary dwelling. A homeowner quoted an impact fee for a basement conversion should ask which statute authorizes it.
Local provisions identified for follow-up
Answer capsule
The table below records provisions identified in July 2026 for follow-up against Utah Code §10-21-304, which took effect on October 1, 2026. These dated records do not establish the city’s current adoption or compliance status. Recheck the adopted ordinance and any uncodified amendments before relying on a listed rule or fee.
| Jurisdiction | Local provision | Statutory subsection | Note |
|---|---|---|---|
| Cottonwood Heights | Detached ADU is a conditional use, with an $1,100 CUP fee | § 10-21-304(3)(a) — no CUP in a primarily residential zone | No published amendment found in the July 18, 2026 source review |
| Cottonwood Heights | Two additional stalls for every detached ADU, regardless of size | § 10-21-304(3)(c) — at most one assigned space below 650 sq ft | Potential conflict noted in the July 18 source check; current rule not rechecked. The issue is specific to units under 650 sq ft. |
| Provo | Detached ADUs limited to the existing ADU Overlay | § 10-21-304(1)(a) — must be permitted on any qualifying lot where a single-family dwelling is a permitted use | No adopted implementing ordinance verified in the July 18, 2026 source review |
Source: municipal codes and official city guidance as cited in each jurisdiction record; Utah Code § 10-21-304. Compiled by Utah ADU Builders Research, July 18, 2026.
What is not on this list, and why. Ogden’s 800 sq ft cap and Salt Lake City’s 1,000 sq ft cap are lawful. Section 10-21-304(4)(a)(i) expressly preserves local regulations governing structure size and dimension. A numeric size cap is not a conflict.
One question worth asking, not yet an answer. Lehi applies § 26.030 to detached units, and § 26.030(D) excludes ADUs from areas on the city’s ADU Restricted Area Map. The 25% area-based exclusion in § 10-21-303(3)(f) applies to internal units only. Section 10-21-304(4)(f) lets a city prohibit a detached ADU where that unit lacks adequate utility access — unit-specific language rather than a blanket map. How a mapped exclusion interacts with a unit-specific utility test is a question for the city, and we raise it as a question rather than a finding.
For the source-checked comparison of named plan lists, sizes and citations, see the Utah pre-approved plan source review.
How we built and verified this
Answer capsule
Every legal rule and jurisdiction value intended for publication traces to a statute, an adopted municipal code, a signed ordinance, or an official government page, and each carries the date we read it. Secondary reporting appears only in labeled implementation-status notes and is never used to establish statutory text.
- Statutes
- We read the full published text of Utah Code §§ 10-21-101, 10-21-102, 10-21-303 and 10-21-304 from the Legislature’s code database. We read the enrolled text of S.B. 284 (2026), § 10-2-301, § 11-36a-202, and the Office of Legislative Research and General Counsel’s June 3, 2025 county classification list.
- Municipal rules
- For each jurisdiction we opened the adopted code section or the city’s own published guidance, recorded the exact section number with any ordinance and amendment date shown, and noted the date we read it. Where a code publisher’s version might lag a recent adoption, we name the document we relied on.
- Source hierarchy
- We identify for every record whether it is an adopted code, a signed ordinance, official city guidance, an official proposal, or secondary implementation reporting. Proposals and reporting are not presented as current adopted law.
- What we do with gaps
- A missing rule is not a prohibition, and an absent fee is not a free permit. When a source does not resolve a field, the record says “no clear public rule found.” We do not infer a value from a neighboring city, from a prior code version, or from what a rule probably is.
- What we exclude
- We reviewed a 2023–24 county survey on ADU interest and did not use it. Its samples were 11 and 17 respondents, which cannot support a published statistic about anything. We name the exclusion so it is clear the source was considered and rejected.
- Editorial independence
- Utah ADU Builders operates commercial ADU-planning pages elsewhere on this site. This research page contains no lead form, referral link, paid placement, sponsored ranking, or affiliate link.
What this data shows — and what it does not
This page compares published law and official guidance. It does not tell you whether a particular parcel is buildable.
- It does not confirm eligibility for your lot. Zoning overlays, easements, slope, buildable area, historic review, utility capacity, existing violations and fire access can all control an outcome the ordinance appears to permit.
- “Will need to change” is our reading, not a ruling. We compared published local text against published statutory text. A city, a city attorney or a court could read either differently.
- Municipal codes lag adoption. Code publishers post disclaimers that their versions may not reflect the most recent legislation. Where a city has adopted an ordinance not yet codified, the adopted ordinance controls.
- Coverage is incomplete. This is a growing verified set, not a statewide census. Most towns and most unincorporated areas are not yet covered.
- Rows age at different rates. Each record carries its own verification date. No single freshness claim covers the whole page.
- Development agreements can override. Section 10-21-304(5)(b) preserves detached-ADU restrictions in any development agreement a municipality signed on or before May 6, 2026.
- This is educational, not legal advice. For a decision with money attached, confirm the current rule with the jurisdiction’s planning department and involve a Utah land use attorney where the question is contested. The Utah Office of the Property Rights Ombudsman is a free state resource for land use questions.
These rules do not establish a construction budget. Compare Utah ADU planning cost ranges by project type before deciding what to pursue.
Why this matters now
The October 1, 2026 state requirement is now in effect. Local codes, application guidance and fee pages may be updated on different schedules. The city records on this page show what was verified on each record’s date; they are not a continuously current adoption roster. Before commissioning plans or paying an application fee, confirm the current adopted ordinance and application path with the relevant planning department.
This implementation timeline answers where an ADU may be permitted, not what one contributes to property value. For the separate appraisal evidence, see what the evidence says about ADUs and home values.
There is a state reporting system, and it is worth understanding precisely what it does. Under § 10-21-202(2)(b)(iv), every specified municipality must annually report to the Division of Housing and Community Development the number of internal and detached ADUs for which it issued a building permit or a license to rent, and the Division posts those reports publicly. Noncompliance carries real consequences: transportation funding restrictions, plus fees to the Olene Walker Housing Loan Fund of $250 per day, rising to $500 per day for a consecutive-year failure. For primary-source data on those reports, see Utah ADU Permit Data: Sources, Counts, and the Gaps.
What that system does not produce is a normalized, continuously current, city-by-city picture of § 10-21-304 implementation. It captures permit counts once a year on a reporting cycle. It does not tell a homeowner in August whether their city has amended its ordinance yet.
For a homeowner, the practical step is to confirm the rules that apply to the property’s jurisdiction, zoning and proposed ADU type. A city website or an older source snapshot may lag an adopted amendment. For legislative history and the dated municipal implementation record, see the Utah SB284 Detached ADU Tracker at Utah SB284 Detached ADU Tracker.
Frequently asked questions
- Are ADUs legal in Utah?
- A qualifying internal ADU is a permitted use in any area zoned primarily for residential use, subject to applicable building, health and fire codes and the conditions § 10-21-303 authorizes. The detached-ADU requirement in §10-21-304 has applied since October 1, 2026 and requires specified municipalities to adopt regulations permitting them on qualifying lots.
- Which Utah cities must allow detached ADUs?
- Specified municipalities, defined at Utah Code § 10-21-101(25): a city of the first, second, third or fourth class, or a city of the fifth class with 5,000 or more residents located in a county of the first, second or third class. Ten of Utah's 29 counties meet that second condition.
- Does my city over 5,000 residents automatically have to comply?
- No. A fifth-class city of 6,000 residents in a fourth-, fifth- or sixth-class county — Carbon, Sanpete, Uintah, Wasatch and others — falls outside § 10-21-101(25)(b). Municipal class comes first, and a population estimate alone does not establish legal class.
- What is the minimum lot size for a detached ADU in Utah?
- Since October 1, 2026, a specified municipality must permit one on a lot or parcel of 11,000 square feet or larger containing a single-family dwelling where single-family dwellings are permitted. Cities may allow smaller lots, and some do. Salt Lake City sets no minimum lot size for an ADU at all.
- Do I have to live on the property to have an ADU in Utah?
- Often yes, and the details vary. For internal ADUs, owner occupancy is built into the statutory definition of primary dwelling, and § 10-21-303(3)(j) separately lets a city bar renting a unit where the dwelling is not the owner's primary residence. For detached ADUs, § 10-21-304(4)(c) lets a city require the owner to live in either unit. Every jurisdiction we have verified so far requires it, with meaningfully different exceptions.
- Can a Utah ADU be used as an Airbnb?
- It depends on the jurisdiction and the unit type. State law lets a municipality prohibit internal-ADU rentals shorter than 30 consecutive days and detached-ADU rentals shorter than 90 consecutive days. Salt Lake City and Cottonwood Heights prohibit short-term rental of ADUs outright. Lehi lets a homeowner hold both permits but activate only one at a time.
- How many parking spaces does a Utah ADU require?
- For internal ADUs, a city may require one additional space, and none where the ordinance already requires four off-street spaces. For detached ADUs, § 10-21-304 caps assigned parking at two spaces for a unit of 650 square feet or larger and one space below that size. Local requirements vary within those ceilings.
- Can a city require a conditional use permit for a detached ADU after October 1, 2026?
- No, for a covered detached ADU in a primarily residential zone; Section 10-21-304(3)(a) prohibits it. The July 18, 2026 Cottonwood Heights source review recorded a conditional-use requirement and a $1,100 fee. That record has not been recertified after the law took effect; confirm the current adopted ordinance with the city.
- Can I convert my existing detached garage into an ADU?
- Section 10-21-304(2)(b) requires a covered city's regulation to include a process for converting a legally constructed accessory structure into a detached ADU, subject to setback requirements and building, health and fire codes. Section 10-21-304(4)(d) separately lets the city require replacement of any parking spaces the garage provided. Salt Lake City already permits conversion of an accessory building that exceeds its height limit and lets it keep its existing setbacks unless the conversion adds an expansion.
- Does an 11,000 square foot lot guarantee ADU approval?
- No. It clears one statutory condition. Setbacks, height, lot coverage, buildable area, utility access and capacity, building and fire codes, easements, owner occupancy and other lawful local standards still apply.
- Can an HOA prohibit an ADU in Utah?
- For internal ADUs, Utah's Community Association Act limits an association's ability to prohibit the rental or construction of a qualifying unit that complies with applicable land use and code requirements. Those provisions do not establish the same rule for detached units. Section 10-21-304(5)(b) separately preserves detached-ADU restrictions in a development agreement a municipality signed on or before May 6, 2026 — which is how a master-planned community can lawfully be stricter than its city. Confirm your specific covenants with counsel or the Office of the Property Rights Ombudsman.
- How often is this page updated?
- Review schedule: state-law changes trigger a review. City records are updated only after the relevant adopted ordinance or official source is checked; each record retains its own verification date.
How to cite this page
Tables on this page are plain HTML and may be copied; each carries a source and verification line directly beneath it. Every statute and municipal code referenced is linked to its issuing source so the underlying material can be checked independently.
Utah ADU Builders Research. “Utah ADU Laws by City.” Utah ADU Builders Research. State law checked ; jurisdiction records carry individual source dates. https://utahadubuilders.com/research/utah-adu-rules-by-city
Sources
Utah statutes and legislative materials
- Utah Code § 10-21-101, Definitions (specified municipality, internal and detached ADU, primary dwelling) — le.utah.gov/xcode/Title10/Chapter21/10-21-S101.html
- Utah Code § 10-21-102, Applicability — le.utah.gov/xcode/Title10/Chapter21/10-21-S102.html
- Utah Code § 10-21-202, Moderate income housing report — contents and penalties — le.utah.gov/xcode/Title10/Chapter21/10-21-S202.html
- Utah Code § 10-21-303, Internal accessory dwelling units (effective November 6, 2025) — le.utah.gov/xcode/Title10/Chapter21/10-21-S303.html
- Utah Code § 10-21-304, Detached accessory dwelling units (effective October 1, 2026; enacted by Chapter 166, 2026 General Session) — le.utah.gov/xcode/Title10/Chapter21/10-21-S304.html
- Utah Code § 10-2-301, Classification of municipalities according to population — le.utah.gov/xcode/Title10/Chapter2/10-2-S301.html
- Utah Code § 10-2-302, Change of class of municipality — le.utah.gov/xcode/Title10/Chapter2/10-2-S302.html
- Utah Code § 11-36a-202, Prohibitions on impact fees (internal ADU exemption at subsection (2)(a)(vi)) — le.utah.gov/xcode/Title11/Chapter36A/11-36a-S202.html
- S.B. 284, “Local Land and Water Modifications,” 2026 General Session, enrolled — le.utah.gov/Session/2026/bills/enrolled/SB0284.pdf
- H.B. 82, “Single-Family Housing Modifications,” 2021 General Session, enrolled
- “Current County Classifications,” June 3, 2025 — Office of Legislative Research and General Counsel — le.utah.gov/lrgc/publications.htm
State agency guidance
- Accessory Dwellings (ADUs) and other dwelling types — Utah Office of the Property Rights Ombudsman — propertyrights.utah.gov/find-the-law/legal-topics/adu/
Municipal codes and official guidance
- Lehi City Development Code Chapter 26 (detached-ADU section amended July 14, 2026) — lehi-ut.gov … Development-Code.pdf
- Salt Lake City Code § 21A.40.200 (Ord. 17-23, 2023; Ord. 53-18, 2018) — codelibrary.amlegal.com …
- Ogden City Code § 15-13-39 (Ord. 2016-2; amended by Ord. 2024-12, May 7, 2024) — codelibrary.amlegal.com … and Ogden ADU permit application
- Cottonwood Heights official Accessory Dwelling Units page — cottonwoodheights.utah.gov …; CH Code § 19.75.050
- Provo City ADU page and June 2026 eligibility-expansion notice — provo.gov …
- Orem City Council and Planning Commission notices, July 2026
- River Heights ADU code draft (riverheights.gov)
- Salt Lake County Municipal Services District Planning and Development Services, “Recommended Amendments to County Code Chapter 19.15,” 2024 Moderate Income Housing Implementation
Reporting
- “Utah County cities prepare for statewide detached ADU changes,” Daily Herald, July 15, 2026
Change log
- — page update and source review
- Updated the page for the public release, confirmed the operative date of § 10-21-304, replaced pre-effective-date language, and labeled earlier city records as dated snapshots. This update does not recertify the city records.
- — rebuilt research record
- Read and verified Utah Code § 10-21-304 in full, including the 11,000 sq ft threshold, the conditional-use prohibition, the 650 sq ft parking tiers, the 90-day detached rental floor, the mandatory accessory-structure conversion process, and the May 6, 2026 development-agreement carve-out. Verified the two-clause “specified municipality” definition at § 10-21-101(25) and confirmed it contains no metro-township clause. Verified the internal-ADU impact-fee prohibition at § 11-36a-202(2)(a)(vi). Verified the state moderate-income-housing ADU reporting requirement at § 10-21-202(2)(b)(iv). Established that § 10-21-304 does not reach unincorporated county land. Confirmed that local numeric size caps are preserved by § 10-21-304(4)(a)(i), and removed Ogden’s 800 sq ft and Salt Lake City’s 1,000 sq ft limits from the provisions-to-watch table. Added complete jurisdiction records for Lehi, Salt Lake City, Ogden and Cottonwood Heights, and status records for Provo, Orem, River Heights and unincorporated Salt Lake County. Documented the unresolved height-table threshold in Lehi Development Code § 26.070.
- — initial publication
- First published version covering 15 jurisdictions sourced to city ordinances and ADU pages, cross-walked against Utah Code §§ 10-21-303 and 10-21-304.